Etching method and plasma treatment device

Abstract

This etching method comprises: (a) a step for providing a substrate on a substrate support part in a chamber; (b) a step for exposing the substrate to a first treatment gas including hydrogen fluoride gas; and (c) a step for exposing the substrate to plasma generated from a second treatment gas while supplying an electrical bias to the substrate support part after (b), the second treatment gas including at least one inert gas selected from the group consisting of noble gases and nitrogen gas.

Description

Etching method and plasma processing apparatus

[0001] SUMMARY OF THE INVENTION Exemplary embodiments of the present disclosure relate to an etching method and a plasma processing apparatus.

[0002] Patent Document 1 discloses a method for etching a region made of silicon oxide. The method includes step (a) of exposing a substrate having a region made of silicon oxide to plasma of a process gas containing a fluorocarbon gas. In step (a), the region is etched and a deposit containing a fluorocarbon is formed on the region. The method includes step (b) of etching the region with fluorocarbon radicals contained in the deposit. Steps (a) and (b) are repeated alternately.

[0003] JP 2015-173240 A

[0004] The present disclosure provides an etching method and a plasma processing apparatus that can improve the etching rate.

[0005] In one exemplary embodiment, an etching method includes: (a) providing a substrate on a substrate support in a chamber; (b) exposing the substrate to a first process gas comprising hydrogen fluoride gas; and (c) after (b), exposing the substrate to a plasma generated from a second process gas while supplying an electrical bias to the substrate support, the second process gas comprising at least one inert gas selected from the group consisting of a noble gas and nitrogen gas.

[0006] According to one exemplary embodiment, an etching method and a plasma processing apparatus capable of improving an etching rate are provided.

[0007] FIG. 1 is a diagram illustrating an example of the configuration of a plasma processing system. FIG. 2 is a diagram illustrating an example of the configuration of an inductively coupled plasma processing apparatus. FIG. 3 is a flowchart of an etching method according to an exemplary embodiment. FIG. 4 is a partially enlarged view of an example substrate to which the method of FIG. 3 can be applied. FIG. 5 is a cross-sectional view illustrating a process of the etching method according to an exemplary embodiment. FIG. 6 is a cross-sectional view illustrating a process of the etching method according to an exemplary embodiment. FIG. 7 is a partially enlarged plan view of an example substrate to which the method of FIG. 3 can be applied. FIG. 8 is a graph illustrating an example of the relationship between the number of cycles and the etching amount. FIG. 9 is a graph illustrating an example of the relationship between the film type and the etching amount. FIG. 10 is a flowchart of an etching method according to an exemplary embodiment. FIG. 11 is a cross-sectional view illustrating a process of the etching method according to an exemplary embodiment. FIG. 12 is a cross-sectional view illustrating a process of the etching method according to an exemplary embodiment. FIG. 13 is a cross-sectional view illustrating a process of the etching method according to an exemplary embodiment. FIG. 14 is a timing chart illustrating an example of the time changes in power and process gas supplied to a plasma processing apparatus.

[0008] Various exemplary embodiments will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0009] FIG. 1 is a diagram illustrating an exemplary configuration of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space and at least one gas exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20 (described later), and the gas exhaust port is connected to an exhaust system 40 (described later). The substrate support 11 is disposed in the plasma processing space and has a substrate support surface for supporting a substrate.

[0010] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma generated in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), surface wave plasma (SWP), or the like. Various types of plasma generators may be used, including alternating current (AC) plasma generators and direct current (DC) plasma generators. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency in the range of 100 kHz to 10 GHz. Thus, AC signals include radio frequency (RF) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0011] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 may be implemented by, for example, a computer 2a. The processing unit 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. This program may be stored in the storage unit 2a2 in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 for execution. The medium may be various storage media readable by the computer 2a or a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a random access memory (RAM), a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0012] The following describes a configuration example of an inductively coupled plasma processing apparatus as an example of the plasma processing apparatus 1. Fig. 2 is a diagram for explaining a configuration example of an inductively coupled plasma processing apparatus.

[0013] The inductively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window 101. The plasma processing apparatus 1 also includes a substrate support 11, a gas inlet, and an antenna 14. The substrate support 11 is disposed within the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, a sidewall 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded.

[0014] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting a substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0015] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a bias electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that the annular region 111b may also be provided by another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, at least one RF / DC electrode coupled to an RF power supply 31 and / or a DC power supply 32, which will be described later, may be disposed within the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple bias electrodes. Alternatively, the electrostatic electrode 1111b may function as a bias electrode. Therefore, the substrate support 11 includes at least one bias electrode.

[0016] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one cover ring. The edge rings are formed of a conductive or insulating material, and the cover rings are formed of an insulating material.

[0017] The substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the backside of the substrate W and the central region 111a.

[0018] The gas inlet is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. In one embodiment, the gas inlet includes a center gas injector (CGI) 13. The center gas injector 13 is disposed above the substrate support 11 and attached to a central opening formed in the dielectric window 101. The center gas injector 13 has at least one gas supply port 13a, at least one gas flow path 13b, and at least one gas inlet port 13c. The process gas supplied to the gas supply port 13a passes through the gas flow path 13b and is introduced into the plasma processing space 10s from the gas inlet port 13c. Note that the gas inlet may include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 13.

[0019] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one process gas from a corresponding gas source 21 to the gas inlet through a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of the at least one process gas.

[0020] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one bias electrode and the antenna 14. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generating unit 12. Furthermore, by supplying a bias RF signal to the at least one bias electrode, a bias potential is generated on the substrate W, thereby attracting ions in the formed plasma to the substrate W.

[0021] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to the antenna 14 via at least one impedance matching circuit and is configured to generate a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14.

[0022] The second RF generator 31b is coupled to at least one bias electrode via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power). The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one bias electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0023] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is connected to at least one bias electrode and configured to generate a bias DC signal. The generated bias DC signal is applied to the at least one bias electrode.

[0024] In various embodiments, the bias DC signal may be pulsed. In this case, a sequence of voltage pulses is applied to at least one bias electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof. In one embodiment, a waveform generator for generating the sequence of voltage pulses from the DC signal is connected between the bias DC generator 32a and at least one bias electrode. Thus, the bias DC generator 32a and the waveform generator constitute a voltage pulse generator. The voltage pulses may have positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. Note that the bias DC generator 32a may be provided in addition to the RF power supply 31 or may be provided instead of the second RF generator 31b.

[0025] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil arranged coaxially. In this case, the RF power supply 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or separate RF generators may be connected to the outer coil and the inner coil separately.

[0026] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is regulated by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0027] 3 is a flowchart of an etching method according to one exemplary embodiment. The etching method MT1 shown in FIG. 3 (hereinafter referred to as "method MT1") can be performed by the plasma processing apparatus 1 of the above embodiment. The method MT1 can be applied to the substrate W of FIG.

[0028] 4 is a cross-sectional view of an example substrate to which the method of FIG. 3 can be applied. As shown in FIG. 4, in one embodiment, the substrate W may include a first region R1 and a second region R2. The first region R1 may be a mask. The substrate W may not include the first region R1. The first region R1 has at least one opening OP. The at least one opening OP may be a hole or a slit. The first region R1 may have multiple openings OP. The second region R2 may be located below the first region R1. The second region R2 may be a film to be etched. The substrate W may further include an underlayer region UR. The underlayer region UR may be located below the second region R2. Each of the first region R1, the second region R2, and the underlayer region UR may be a film.

[0029] The first region R1 includes a first material. The first material may include a metal or silicon. The metal may be a metal other than tungsten, molybdenum, and titanium. The first material may include ruthenium (Ru).

[0030] The second region R2 includes a second material. The second material is different from the first material. The second material may include at least one selected from the group consisting of silicon, carbon, and a metal. The second material may be silicon oxide (SiO ｘ ), silicon nitride (SiN ｘ The second material may be at least one silicon-containing material selected from the group consisting of silicon oxynitride (SiON) and polysilicon, where x is a positive real number. The second material may be at least one carbon-containing material selected from the group consisting of photoresist (polymer) and amorphous carbon. The second material may include at least one metal selected from the group consisting of tungsten (W), molybdenum (Mo), and titanium (Ti). The second material may be a compound containing a metal element and a non-metal element. The second material may be at least one selected from the group consisting of metal silicide, metal nitride, and metal carbide. The second material may be tungsten silicide (WSi).

[0031] The underlying region UR includes a third material, which is different from the first material and the second material, and may include metal or silicon.

[0032] Method MT1 will be described below with reference to FIGS. 3 to 6, taking as an example a case where method MT1 is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. FIGS. 5 to 6 are cross-sectional views showing a step of an etching method according to one exemplary embodiment. When the plasma processing apparatus 1 is used, method MT1 can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 with a control unit 2. In method MT1, a substrate W on a substrate support 11 arranged in a plasma processing chamber 10 is processed, as shown in FIG. 2.

[0033] 3, the method MT1 may include steps ST1 to ST5. The steps ST1 to ST5 may be performed in order. The method MT1 may not include step ST3 or step ST5.

[0034] (Step ST1) In step ST1, the substrate W shown in FIG. 4 is provided on the substrate support 11 in the plasma processing chamber 10.

[0035] (Process ST2) In process ST2, the substrate W is exposed to a first process gas containing hydrogen fluoride (HF) gas. In process ST2, plasma does not necessarily have to be generated from the first process gas. The supply of the first process gas may be stopped at the end of process ST2. In process ST2, as shown in FIG. 5 , hydrogen fluoride molecules are adsorbed onto the surface of the substrate W to form an adsorption layer AB. The adsorption layer AB may contain hydrogen fluoride. The hydrogen fluoride molecules are adsorbed onto the surface of the second region R2. The hydrogen fluoride molecules may or may not be adsorbed onto the surface of the first region R1. The adsorption layer AB may be a layer formed by a reaction between hydrogen fluoride and the second region R2. The thickness of the adsorption layer AB increases over time and may saturate at a certain value.

[0036] The first process gas is a mixture of a noble gas and nitrogen (N ２ The first process gas may further include at least one inert gas selected from the group consisting of hydrogen fluoride gas, hydrogen fluoride gas, and argon (Ar) gas. Examples of noble gases in this specification include argon (Ar) gas, helium (He) gas, xenon (Xe) gas, and neon (Ne) gas. The flow rate of hydrogen fluoride gas may be the highest among all the gases included in the first process gas. The inert gas that may be included in the first process gas may be the same as or different from the inert gas included in the second process gas in step ST4. The first process gas does not necessarily need to include any fluorine-containing gas other than hydrogen fluoride gas.

[0037] The duration of step ST2 may be 0.1 to 100 seconds, or may be 30 to 80 seconds.

[0038] In step ST2, the temperature of the substrate support 11 may be controlled to a range of −10° C. to 80° C., or may be controlled to a range of 10° C. to 80° C. In such a range, the adsorption of hydrogen fluoride to silicon oxide is not promoted. Therefore, in step ST4, the etching rate of silicon oxide is smaller than the etching rate of silicon nitride.

[0039] In step ST2, the pressure inside plasma processing chamber 10 may be 100 mTorr (13 Pa) or more, or 1000 mTorr (130 Pa) or less.

[0040] Step ST2 may be performed as follows: The gas supply unit 20 supplies a first processing gas into the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generation unit 12 so that plasma is not generated.

[0041] (Step ST3) In step ST3, the internal space of the plasma processing chamber 10 is purged. Purging may be performed by supplying an inert gas into the plasma processing chamber 10, or by evacuating the internal space of the plasma processing chamber 10. Purging may be performed by combining supplying an inert gas and evacuating the internal space of the plasma processing chamber 10.

[0042] (Step ST4) In step ST4, as shown in Fig. 6, the substrate W is exposed to a plasma PL generated from a second process gas while an electric bias is supplied to the substrate support 11. The second process gas may be different from the first process gas in step ST2. The second process gas may be a mixture of a noble gas and nitrogen (N ２ The second process gas may contain at least one inert gas selected from the group consisting of halogen gases. The inert gas may have the highest flow rate among all the gases contained in the second process gas. The second process gas may not contain a halogen gas.

[0043] In step ST4, an electric bias causes ions IN in the plasma PL to collide with the adsorption layer AB. The ions IN may be ions of an inert gas. The collision energy of the ions IN causes a reaction between the adsorption layer AB and the substrate W (second region R2), thereby etching the substrate W (second region R2). As a result, a recess RS is formed in the substrate W (second region R2). In step ST4, the etching may be stopped when the adsorption layer AB is depleted. The supply of the second process gas may be stopped at the end of step ST4.

[0044] The duration of step ST4 may be shorter than the duration of step ST2. The duration of step ST4 may be ⅓ or less of the duration of step ST2. The duration of step ST4 may be 0.1 to 100 seconds, or 0.1 to 20 seconds. Since the ions IN are caused to collide with the substrate W (second region R2) by the electric bias, large collision energy of the ions IN is imparted to the substrate W (second region R2). Therefore, even if the duration of step ST4 is shortened, a high etching rate can be obtained.

[0045] In step ST4, the temperature of the substrate support 11 may be controlled to a range of -10°C to 80°C, or may be controlled to a range of 10°C to 80°C.

[0046] The pressure in the plasma processing chamber 10 at step ST4 may be lower than the pressure in the plasma processing chamber 10 at step ST2. At step ST4, the pressure in the plasma processing chamber 10 may be 10 mTorr (1.3 Pa) or higher. Alternatively, the pressure in the plasma processing chamber 10 may be 100 mTorr (13 Pa) or lower.

[0047] Step ST4 may be performed as follows. First, the gas supply unit 20 supplies the second process gas into the plasma processing chamber 10. Next, the plasma generation unit 12 generates plasma PL from the second process gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generation unit 12 to generate plasma PL. The control unit 2 controls the power supply 30 to supply an electric bias to the substrate support unit 11.

[0048] (Step ST5) In step ST5, steps ST2 to ST4 are repeated. This increases the etching amount of the second region R2, thereby deepening the recess RS. In step ST2 of step ST5, an adsorption layer AB may be formed on the sidewall and bottom of the recess RS. In step ST4 of step ST5, ions IN collide with the adsorption layer AB on the bottom of the recess RS, but are less likely to collide with the adsorption layer AB on the sidewall of the recess RS.

[0049] According to the method MT1, the etching rate of the substrate W (second region R2) can be improved in step ST4. The mechanism is presumed to be, but is not limited to, as follows. In step ST2, hydrogen fluoride molecules are adsorbed onto the surface of the substrate W to form an adsorption layer AB. The adsorption layer AB may be a layer formed by reaction of hydrogen fluoride with the substrate W (second region R2). Thereafter, in step ST4, an electric bias causes ions IN in the plasma PL to collide with the adsorption layer AB. The collision energy of the ions IN causes a reaction between the adsorption layer AB and the substrate W (second region R2), thereby etching the substrate W (second region R2).

[0050] Furthermore, in the method MT1, no film is formed by plasma CVD in step ST2. This reduces the influence of loading on the dimensions (critical dimension: CD) and depth of the recesses RS. Furthermore, the in-plane uniformity of the dimensions (CD) and depth of the recesses RS can be improved.

[0051] Furthermore, in the method MT1, deposits are less likely to adhere to the opening OP in the step ST2, so clogging of the opening OP can be suppressed.

[0052] FIG. 7 is a partially enlarged plan view of an example substrate W to which method MT1 can be applied. An XYZ Cartesian coordinate system is shown in FIG. 7. A first direction X and a second direction Y are directions along the main surface of the substrate W. A third direction Z is a direction perpendicular to the main surface of the substrate W. The substrate W shown in FIG. 7 includes a second region R2 as a film to be etched. The second region R2 has at least one recess RS. The recess RS corresponds to the opening OP in the first region R1. The recess RS may be formed by etching the second region R2 through the opening OP before step ST2.

[0053] The recess RS has a first pair of sidewalls SW1 that face each other in the first direction X with a first width XCD, and a second pair of sidewalls SW2 that face each other in the second direction Y with a second width YCD. The second direction Y is perpendicular to the first direction X. The second width YCD is greater than the first width XCD. The recess RS may have, for example, an elliptical shape in the XY plane that includes the first direction X and the second direction Y.

[0054] 7, in step ST2, an adsorption layer AB is formed in the recess RS. The adsorption layer AB may be formed on the sidewalls and bottom of the recess RS. The adsorption layer AB may be formed on the first sidewall pair SW1 and the second sidewall pair SW2.

[0055] In step ST4, the first sidewall pair SW1 and the second sidewall pair SW2 are etched. The etching causes the recess RS to expand in the XY plane including the first direction X and the second direction Y (see the recess RS indicated by the dashed line in FIG. 7 ). The etching amount YEA of each of the second sidewall pair SW2 is greater than the etching amount XEA of each of the first sidewall pair SW1. This is believed to be because the flux of ions IN incident on each of the second sidewall pair SW2 is greater than the flux of ions IN incident on each of the first sidewall pair SW1.

[0056] Various experiments performed to evaluate Method MT1 are described below, but the experiments described below are not intended to limit the present disclosure.

[0057] (First Experiment) In the first experiment, a substrate was first provided on a substrate support in a chamber of a plasma processing apparatus (step ST1). ２ A film was formed. Next, a first process gas containing HF gas and Ar gas was supplied onto the substrate without generating plasma (step ST2). The duration of step ST2 was 60 seconds. Next, argon gas was supplied into the chamber to purge the internal space of the chamber (step ST3). The duration of step ST3 was 30 seconds. Next, plasma generated from Ar gas was supplied to the substrate while an electric bias was supplied to the substrate support (step ST4). The duration of step ST4 was 10 seconds. Next, steps ST2 to ST4 were repeated so that each step was performed three times (number of cycles) (step ST5). The temperature of the substrate support during steps ST2 to ST5 was −5° C.

[0058] (Second Experiment) The second experiment was carried out in the same manner as the first experiment, except that step ST5 was carried out so that the number of cycles was 10.

[0059] (Third Experiment) The third experiment was carried out in the same manner as the first experiment, except that step ST5 was carried out so that the number of cycles was 20.

[0060] (Fourth Experiment) The substrate is SiO ２ A fourth experiment was carried out in the same manner as the first experiment, except that a SiN film was used instead of the membrane.

[0061] (Fifth Experiment) The fifth experiment was carried out in the same manner as the fourth experiment, except that step ST5 was carried out so that the number of cycles was 10.

[0062] (Sixth Experiment) The sixth experiment was carried out in the same manner as the fourth experiment, except that step ST5 was carried out so that the number of cycles was 20.

[0063] (Seventh Experiment) The substrate is SiO ２ The seventh experiment was carried out in the same manner as the second experiment, except that the film was replaced with a photoresist film, and the number of cycles was 10.

[0064] (Eighth Experiment) The eighth experiment was carried out in the same manner as the seventh experiment, except that step ST5 was carried out so that the number of cycles was 20.

[0065] (Ninth Experiment) The substrate is SiO ２ The ninth experiment was carried out in the same manner as the second experiment, except that the film had a polysilicon film instead of the film. The number of cycles was 10.

[0066] (Tenth Experiment) A tenth experiment was carried out in the same manner as the ninth experiment, except that step ST5 was carried out so that the number of cycles was 20.

[0067] (11th Experiment) The substrate is SiO ２ The eleventh experiment was carried out in the same manner as the third experiment, except that the WSi film was used instead of the film. The number of cycles was 20.

[0068] (Results of First Experiment) In each of the first to eleventh experiments, the etching amount of the film included in the substrate was measured. The results are shown in Fig. 8 and Fig. 9. In Fig. 8 and Fig. 9, EX1 to EX11 indicate the measurement results of the first to eleventh experiments, respectively. As shown in Fig. 8, it was found that the etching amount of each film in the first to tenth experiments increased in proportion to the number of cycles. As shown in Fig. 9, the etching amount of the photoresist (PR) film, SiN film, WSi film, SiO ２ It was found that the silicon dioxide film and the polysilicon (Poly-Si) film were most easily etched in this order.

[0069] (Twelfth Experiment) A twelfth experiment was carried out in the same manner as the first experiment, except that the duration of step ST2 was set to 180 seconds and steps ST3 to ST5 were not carried out.

[0070] (Thirteenth Experiment) A thirteenth experiment was carried out in the same manner as the first experiment, except that the duration of step ST4 was set to 30 seconds and steps ST2, ST3 and ST5 were not carried out.

[0071] (14th Experiment) The substrate is SiO ２ A fourteenth experiment was carried out in the same manner as the twelfth experiment, except that a SiN film was used instead of the membrane.

[0072] (15th Experiment) The substrate is SiO２ The fifteenth experiment was carried out in the same manner as the thirteenth experiment, except that a SiN film was used instead of the membrane.

[0073] (Results of the Second Experiment) In each of the 12th to 15th experiments, the etching amount of the film included in the substrate was measured. As a result, the etching amount was 5 nm or less in all cases. It was found that etching did not proceed even if only one of the steps ST2 and ST4 was performed.

[0074] (16th Experiment) In step ST2, CF gas was used instead of HF gas. ４ The 16th experiment was carried out in the same manner as the 2nd experiment, except that a SiO2 gas was used as the substrate. ２ It has a membrane.

[0075] (17th Experiment) In step ST2, CF gas was used instead of HF gas. ４ The 17th experiment was carried out in the same manner as in the 5th experiment, except that the gas was used. The substrate had a SiN film.

[0076] (18th Experiment) In step ST2, CF gas was used instead of HF gas. ４ Experiment 18 was carried out in the same manner as Experiment 7, except that gas was used. The substrate had a photoresist film.

[0077] (19th Experiment) In step ST2, CF gas was used instead of HF gas. ４ The 19th experiment was carried out in the same manner as in Experiment 9, except that a gas was used. The substrate had a polysilicon film.

[0078] (Results of the Third Experiment) In each of the 16th to 19th experiments, the etching amount of the film included in the substrate was measured. As a result, the etching amount was almost 0 nm in all cases. It was found that etching does not proceed unless HF gas is used in the step ST2.

[0079] (Duration of Step ST2) Etching was performed in the same manner as in Experiment 2 or Experiment 5, except that the duration of Step ST2 was changed to 10 seconds, 30 seconds, and 90 seconds, and the etching amount of the film contained in the substrate was measured. As a result, up to the duration of Step ST2 of 60 seconds, the etching amount increased as the duration of Step ST2 was increased. When the duration of Step ST2 was longer than 60 seconds, the etching amount hardly changed even when the duration of Step ST2 was increased. This indicates that the formation of an adsorption layer or reaction layer of HF gas automatically stops due to a self-limiting reaction.

[0080] (Duration of Step ST4) Etching was performed in the same manner as in Experiment 2 or Experiment 5, except that the duration of Step ST4 was changed to 2 seconds, 5 seconds, and 20 seconds, and the etching amount of the film contained in the substrate was measured. As a result, up to the duration of Step ST4 of 10 seconds, the etching amount increased as the duration of Step ST4 was increased. When the duration of Step ST4 was longer than 10 seconds, the etching amount hardly changed even when the duration of Step ST4 was increased. This indicates that etching automatically stops when the adsorption layer or reaction layer of HF gas is depleted.

[0081] 10 is a flowchart of an etching method according to one example embodiment. The etching method MT2 shown in FIG. 10 (hereinafter referred to as "method MT2") can be performed by the plasma processing apparatus 1 of the above embodiment. The method MT2 can be applied to the substrate W of FIG.

[0082] Method MT2 will be described below with reference to FIGS. 4 and 10 to 13, taking as an example a case where method MT2 is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. FIGS. 11 to 13 are cross-sectional views showing steps of an etching method according to one exemplary embodiment. When the plasma processing apparatus 1 is used, method MT2 can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 with the control unit 2. In method MT2, a substrate W on a substrate support 11 disposed in a plasma processing chamber 10 is processed, as shown in FIG. 2.

[0083] 10 , the method MT2 may include steps ST1, ST21, ST41, and ST5. The steps ST1, ST21, ST41, and ST5 may be performed in this order. The method MT2 does not necessarily include step ST5.

[0084] (Process ST1) In process ST1, the substrate W shown in FIG. 4 is provided on the substrate support 11 in the plasma processing chamber 10. Then, as shown in FIG. 11, the second region R2 is etched through the opening OP in the first region R1 by a plasma PL1 generated from a processing gas. As a result, a substrate W including a second region R2 having at least one recess RS is provided on the substrate support 11. The recess RS may have a first portion RS1 and a second portion RS2 on the first portion RS1. The first portion RS1 may have a first sidewall SW11. The first portion RS1 may have a bottom of the recess RS. The second portion RS2 may have a second sidewall SW12. The second portion RS2 may have an upper end of the recess RS. In the first portion RS1, the dimension (CD) of the recess RS may gradually decrease from the upper end to the lower end of the first portion RS1. The process gas for generating the plasma PL1 may include a fluorine-containing gas. Examples of the fluorine-containing gas include a fluorocarbon gas, a hydrofluorocarbon gas, and a hydrogen fluoride gas.

[0085] A protective film PF may be formed on the second sidewall SW12. The protective film PF may be formed on the first region R1. The protective film PF may be formed simultaneously with the recess RS, or may be formed after the recess RS is formed. When the process gas contains a fluorocarbon gas or a hydrofluorocarbon gas, the recess RS and the protective film PF may be formed simultaneously. In this case, the protective film PF contains carbon and fluorine. When the process gas contains hydrogen fluoride gas, the recess RS may be formed without forming the protective film PF. In this case, after the recess RS is formed, the protective film PF may be formed by, for example, ALD or CVD.

[0086] (Process ST21) Process ST21 may be performed in the same manner as process ST2 of method MT1. In process ST21, as shown in FIG. 12 , the second region R2 is exposed to a third process gas containing hydrogen fluoride gas while no electric bias is supplied to the substrate support 11 or while a first level electric bias is supplied to the substrate support 11. The third process gas may be the same as the process gas used in process ST1. The third process gas may further contain a fluorocarbon gas or a hydrofluorocarbon gas. In process ST21, plasma may not be generated from the third process gas. In process ST21, as shown in FIG. 12 , the surface of the first sidewall SW11 may be modified. As a result, a modified layer MR is formed on the surface of the first sidewall SW11. When the protective film PF is formed on the second sidewall SW12, the modified layer MR is not formed on a portion of the surface of the second sidewall SW12 that is covered with the protective film PF. The modified layer MR may be the adsorption layer AB shown in FIG.

[0087] (Step ST41) Step ST41 may be performed in the same manner as step ST4 of method MT1. In step ST41, as shown in FIG. 13 , while supplying a second level of electric bias to the substrate support 11, the second region R2 is exposed to plasma PL generated from a fourth process gas containing hydrogen fluoride gas. The fourth process gas may be the same as the third process gas. The fourth process gas may further contain a fluorocarbon gas or a hydrofluorocarbon gas. The second level of the electric bias supplied to the substrate support 11 in step ST41 is greater than the first level of the electric bias that may be supplied to the substrate support 11 in step ST21. In step ST41, as shown in FIG. 13 , the surface (modified layer MR) of the first sidewall SW11 modified in step ST21 may be removed. This etches the first sidewall SW11.

[0088] (Step ST5) In step ST5, a cycle including step ST21 and step ST41 is repeated. Each cycle may further include an etching step included in step ST1 before step ST21.

[0089] From step ST21 to step ST41, the hydrogen fluoride gas may be continuously supplied into the plasma processing chamber 10. The hydrogen fluoride gas may be continuously supplied into the plasma processing chamber 10 throughout all of the above cycles.

[0090] According to the method MT2, in step ST21, a modified layer MR can be formed in the first portion RS1 near the bottom of the recess RS. As a result, in step ST41, etching of the first portion RS1 near the bottom of the recess RS can be accelerated. This improves the etching rate of the recess RS having a high aspect ratio. Furthermore, since the first sidewall SW11 can be etched in step ST41, the dimension (CD) of the recess RS at the bottom of the recess RS can be increased.

[0091] 14 is a timing chart showing an example of temporal changes in power and process gas supplied to the plasma processing apparatus. This timing chart relates to steps ST1, ST21, ST41, and ST5. The plasma processing apparatus 1 may be supplied with source power and bias power. The source power may be high-frequency power HF applied to the counter electrode (upper electrode). The bias power may be high-frequency power LF or DC bias applied to an electrode in the main body 111 of the substrate support 11.

[0092] As shown in FIG. 14 , the source power and the bias power may be applied periodically with a period CY. The period CY may include a first period PA, a second period PB, and a third period PC. The second period PB is a period after the first period PA. The third period PC is a period after the second period PB. The first period PA and the second period PB in the first period CY correspond to the etching step included in process ST1. In the etching step included in process ST1, a recess RS may be formed as shown in FIG. 11 . The third period PC corresponds to process ST21. In process ST21, a modified layer MR may be formed as shown in FIG. 12 . The first period PA and the second period PB after the third period PC correspond to process ST41. In process ST41, the first sidewall SW11 may be etched as shown in FIG. 13 . The third period PC and the subsequent period in the second period CY correspond to process ST5.

[0093] During the first period PA, the power level of the source power may be maintained at level H2, and the power level of the bias power may be maintained at level H1. Level H1 is lower than level H2. During the second period PB, the power level of the source power may be maintained at level L2, and the power level of the bias power may be maintained at level H1. Level L2 is lower than level H2. Level L2 may be 0 W. During the third period PC, the power level of the source power may be maintained at level L2, and the power level of the bias power may be maintained at level L1. Level L1 is lower than level H1. Level L1 may be 0 W.

[0094] A DC bias may be supplied to the substrate support 11 as the electric bias instead of the high frequency power LF. The DC bias may include a voltage pulse. When the electric bias is bias RF power, the level of the electric bias is the power level (effective value) of the bias RF power. When the electric bias includes a voltage pulse, the level of the electric bias is the absolute value of the negative voltage level of the voltage pulse.

[0095] 14, the processing gas supplied to the plasma processing apparatus may be continuously supplied over the entire cycle CY. The processing gas may include a fluorocarbon gas, a hydrofluorocarbon gas, and a hydrogen fluoride gas.

[0096] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. Furthermore, elements in different embodiments may be combined to form other embodiments.

[0097] Various exemplary embodiments included in the present disclosure are now described in [E1] to [E19] below.

[0098] [E1] An etching method comprising: (a) providing a substrate on a substrate support in a chamber; (b) exposing the substrate to a first process gas comprising hydrogen fluoride gas; and (c) after (b), exposing the substrate to a plasma generated from a second process gas while supplying an electrical bias to the substrate support, the second process gas comprising at least one inert gas selected from the group consisting of a noble gas and a nitrogen gas.

[0099] According to the etching method [E1], in (c), the etching rate of the substrate can be improved.

[0100] [E2] The etching method according to [E1], further comprising the step of (d) repeating the steps (b) and (c).

[0101] [E3] The etching method according to [E1] or [E2], wherein the duration of (b) is 0.1 to 100 seconds.

[0102] [E4] The etching method according to any one of [E1] to [E3], wherein the duration of (c) is 0.1 to 100 seconds.

[0103] [E5] The etching method according to any one of [E1] to [E4], wherein the substrate contains at least one selected from the group consisting of silicon, carbon, and metal.

[0104] [E6] The etching method according to [E5], wherein the substrate contains at least one silicon-containing material selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, and polysilicon.

[0105] [E7] The etching method according to [E5], wherein the substrate contains at least one carbon-containing material selected from the group consisting of photoresist and amorphous carbon.

[0106] [E8] The etching method according to [E5], wherein the substrate contains at least one metal selected from the group consisting of tungsten, molybdenum, and titanium.

[0107] [E9] The etching method according to any one of [E1] to [E8], wherein the substrate includes a first region and a second region below the first region, the first region including a first material and having an opening, and the second region including a second material different from the first material.

[0108] In this case, in (b), blocking of the opening can be suppressed.

[0109] [E10] The etching method according to [E9], wherein the second material includes at least one selected from the group consisting of silicon, carbon, and metal.

[0110] [E11] The etching method according to [E9] or [E10], wherein the first material includes a metal other than tungsten, molybdenum, and titanium.

[0111] [E12] The etching method according to any one of [E1] to [E11], further comprising: (e) a step of purging the internal space of the chamber between (b) and (c).

[0112] [E13] The etching method according to any one of [E1] to [E12], wherein in (b), the temperature of the substrate support part is controlled within a range of -10°C to 80°C.

[0113] [E14] The etching method according to any one of [E1] to [E13], wherein the substrate includes an etching target film having at least one recess, the at least one recess having a first pair of sidewalls opposing each other in a first direction with a first width therebetween and a second pair of sidewalls opposing each other in a second direction perpendicular to the first direction with a second width greater than the first width, and wherein in (c), the first pair of sidewalls and the second pair of sidewalls are etched, and an etching amount of the second pair of sidewalls is greater than an etching amount of the first pair of sidewalls.

[0114] [E15] An etching method comprising: (a) providing a substrate, the film to be etched having at least one recess, on a substrate support in a chamber; (b) exposing the film to be etched to a third process gas containing hydrogen fluoride gas while supplying no electrical bias or a first level electrical bias to the substrate support; and (c) after (b), exposing the film to be etched to a plasma generated from a fourth process gas containing hydrogen fluoride gas while supplying a second level electrical bias to the substrate support that is greater than the first level.

[0115] [E16] The etching method according to [E15], wherein the hydrogen fluoride gas is continuously supplied into the chamber from (b) to (c).

[0116] [E17] The etching method according to [E15] or [E16], wherein a cycle including the steps (b) and (c) is repeated.

[0117] [E18] The etching method according to any one of [E15] to [E17], wherein the recess has a first portion and a second portion on the first portion, the first portion has a first sidewall, and the second portion has a second sidewall, (b) includes modifying a surface of the first sidewall, and (c) includes removing the modified surface of the first sidewall.

[0118] [E19] A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber; a gas supply unit configured to supply a first process gas and a second process gas into the chamber, wherein the first process gas includes hydrogen fluoride gas and the second process gas includes at least one inert gas selected from the group consisting of a noble gas and a nitrogen gas; a plasma generation unit configured to generate plasma from the second process gas in the chamber; a power supply for supplying an electric bias to the substrate support; and a controller configured to control the gas supply unit, the plasma generation unit, and the power supply to perform the following steps: (b) exposing the substrate to the first process gas; and (c) after (b), exposing the substrate to the plasma generated from the second process gas while supplying the electric bias to the substrate support.

[0119] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

[0120] 1...plasma processing apparatus, 2...control unit, 10...plasma processing chamber, 11...substrate support unit, 12...plasma generation unit, 20...gas supply unit, 30...power supply, PL...plasma, R2...second region (film to be etched), RS...recess, W...substrate

Claims

1. A method of etching comprising: (a) providing a substrate on a substrate support in a chamber; (b) exposing the substrate to a first process gas comprising hydrogen fluoride gas; and (c) after (b), exposing the substrate to a plasma generated from a second process gas while supplying an electrical bias to the substrate support, the second process gas comprising at least one inert gas selected from the group consisting of noble gases and nitrogen gas.

2. The etching method of claim 1, further comprising the step of: (d) repeating steps (b) and (c).

3. The etching method according to claim 1 or 2, wherein the duration of (b) is 0.1 to 100 seconds.

4. The etching method according to claim 1 or 2, wherein the duration of (c) is 0.1 to 100 seconds.

5. The etching method according to claim 1 or 2, wherein the substrate comprises at least one selected from the group consisting of silicon, carbon and metal.

6. The etching method of claim 5, wherein the substrate comprises at least one silicon-containing material selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, and polysilicon.

7. The etching method of claim 5, wherein the substrate comprises at least one carbon-containing material selected from the group consisting of photoresist and amorphous carbon.

8. The etching method of claim 5, wherein the substrate comprises at least one metal selected from the group consisting of tungsten, molybdenum, and titanium.

9. The etching method of claim 1 or 2, wherein the substrate includes a first region and a second region below the first region, the first region including a first material and having an opening, and the second region including a second material different from the first material.

10. The etching method of claim 9, wherein the second material includes at least one selected from the group consisting of silicon, carbon, and a metal.

11. The etching method of claim 9, wherein the first material comprises a metal other than tungsten, molybdenum, and titanium.

12. The etching method according to claim 1 or 2, further comprising the step of: (e) purging the interior space of the chamber between (b) and (c).

13. The etching method according to claim 1 or 2, wherein in (b), the temperature of the substrate support is controlled within the range of -10°C to 80°C.

14. The etching method according to claim 1 or 2, wherein the substrate includes a film to be etched having at least one recess, the at least one recess having a first pair of sidewalls opposing each other in a first direction and a first width, and a second pair of sidewalls opposing each other in a second direction perpendicular to the first direction and a second width greater than the first width, and wherein in (c), the first pair of sidewalls and the second pair of sidewalls are etched, and an etching amount of the second pair of sidewalls is greater than an etching amount of the first pair of sidewalls.

15. An etching method comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a film to be etched having at least one recess; (b) exposing the film to be etched to a third process gas comprising hydrogen fluoride gas while applying no electrical bias or a first level of electrical bias to the substrate support; and (c) after (b), exposing the film to be etched to a plasma generated from a fourth process gas comprising hydrogen fluoride gas while applying a second level of electrical bias to the substrate support, the second level being greater than the first level.

16. The etching method according to claim 15, wherein the hydrogen fluoride gas is continuously supplied into the chamber from (b) to (c).

17. The etching method according to claim 15 or 16, wherein a cycle including steps (b) and (c) is repeated.

18. The etching method of claim 15 or 16, wherein the recess has a first portion and a second portion on the first portion, the first portion having a first sidewall and the second portion having a second sidewall, (b) includes modifying a surface of the first sidewall, and (c) includes removing the modified surface of the first sidewall.

19. A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber; a gas supply configured to supply a first process gas and a second process gas into the chamber, the first process gas comprising hydrogen fluoride gas and the second process gas comprising at least one inert gas selected from the group consisting of a noble gas and a nitrogen gas; a plasma generation unit configured to generate plasma from the second process gas in the chamber; a power source for supplying an electric bias to the substrate support; and a controller, wherein the controller is configured to control the gas supply unit, the plasma generation unit, and the power source to perform the following steps: (b) exposing the substrate to the first process gas; and (c) after (b), exposing the substrate to the plasma generated from the second process gas while supplying the electric bias to the substrate support.

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